"In my view, it is better to fling open the gates of all our prisons and ask all the inmates to walk out into the warm embrace of their relatives than pardon those who force otherwise decent Nigerians to take to crime as a way of life," Mr Aturu is quoted as saying.

Nuhu Ribadu, Nigeria's former anti-corruption chief and leader of the opposition Action Congress of Nigeria (ACN) party, said the pardon was the "the final nail" in the coffin for fighting corruption in the country, Associated Press news agency reports.

Nigeria is Africa's leading oil producer, but critics say widespread corruption has meant that its wealth has not been used to improve living standards in a country where most people are poor.